Boffins discover dawn of vision in animals

The researchers studied the light-receptive genes in cnidarians, an ancient class of animals that includes corals, jellyfish, and sea anemones, and which have existed for hundreds of millions of years.

“We are the first to analyze these vision genes (opsins) in these early animals. We don’t find them in earlier evolving animals like sponges, so we can put a date on the evolution of light sensitivity in animals,” said David C. Plachetzki, first author and a graduate student at UC Santa Barbara.

“We now have a time frame for the evolution of animal light sensitivity. We know its precursors existed roughly 600 million years ago,” said Plachetzki.

Hydras are predators, and the scientists speculate they use light sensitivity in order to find prey.

Hydra use opsin proteins all over their bodies, but they are concentrated in the mouth area, near the tip of the animal. Hydras have no eyes or light-receptive organs, but they have the genetic pathways to be able to sense light.

Senior author Todd H. Oakley, assistant professor of biology at UCSB, said that there have been only a handful of cases where scientists have documented the very specific mutational events that have given rise to new features during evolution.

Prof. Oakley said that anti-evolutionists have often argued that mutations, which are essential for evolution, can only eliminate traits and cannot produce new features.

“Our paper shows that such claims are simply wrong. We show very clearly that specific mutational changes in a particular duplicated gene (opsin) allowed the new genes to interact with different proteins in new ways. Today, these different interactions underlie the genetic machinery of vision, which is different in various animal groups,” he said.